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network media
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Network Media Flow of Data Sent along BUS in bits (16,32 or 64, depending on type) Sent to NIC buffer, small section of RAM on the NIC MAU (part of NIC) turns bits into electrical signals NIC sends bits across network NIC at other end receives data and puts in computers RAM Bits, Bytes, Parity Bit – binary digit (0 or 1), smallest unit of information used Byte – group of bits (8) Parity – error checking, 8th bit usually for parity check Always 0 – space parity/no parity Always 1 – mark parity Even number of 1’s – even parity Odd number of 1’s – odd parity Parity calculated when transmitted and checked when received Both computers must use same parity system Transmission Speed Speed calculated by Bit Rate Expressed in bits per second (Bps) High-speed transmission abbreviated to kilobits per second (Kbs) Higher speed, mega-bits and giga-bits per second (Mbps & Gbps) Baud Rate – number of signal changes through medium in certain time Serial Transmission One bit sent at a time down one wire Slow transmission Most economical Most widely used Used in network media Parallel Transmission Several bits sent at one time Each bit has own wire on BUS Buses can be 8,16,32 or 64 bits wide Faster transmission More expensive Worthwhile for longer distances Synchronous Serial Transmission Sender and receiver must be synchronised Achieved by sending SYN characters down line before data Asynchronous Serial Transmission Without synchronisation No set delay period between transmission of each character Characters travel individually rather than in blocks as user keys them in As typing is not constant, characters travel irregularly Commonly used for low speed transmission Start and stop bit sent, along with extra bit for parity check Receiving end alerted by start bit in front of transmitted character Stop bit alerts receiving end that bit stream is finished Data Transmission 3 types of communication path: 1.
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